1. Field of the Invention
This invention relates to latch systems of the type used on movable closures and, more particularly, to a latch system that releasably maintains a movable closure in at least one position therefor and through which release and repositioning of the closure element to another position therefor are facilitated.
2. Background Art
Sliding closure elements are used in a wide range of environments. These closure elements are commonly used on delivery vehicles to provide an opening for a user thereof to conveniently access the storage, or front cab, area of the vehicle to facilitate loading and unloading thereof.
In this environment, it is common for users to be carrying one or more packages as the closure element is being manipulated. For example, it is common for a user to unlatch and open one closure element to access a package in one part of the vehicle and, while carrying that package, close and latch the one closure element and unlatch and open another closure element to access a package at another location in the vehicle. It is thus a goal of designers and manufacturers of latch systems and closure elements for this type of vehicle to facilitate safe, one-handed operation of the closure elements as latch systems thereon are latched and unlatched and the closure elements are opened and closed.
It is known to provide latch assemblies which are operable by a graspable handle that is rotatable about a fore and aft axis. In one motion, the user torques the handle to place the latch assembly in an unlatched/released state and in a separate motion translates the closure element from a closed position in a path, that is transverse to the pivot axis of the handle, to an open position. The two separate actions required by the user may make unlatching of the latch assembly and opening of the closure element awkward to carry out.
Another consideration in the design of this type of closure element and latch system is that the entire mechanism may be subjected to relatively severe force application in use. A user balancing a package in one hand may tend to exert a large force in both opening and closing the closure element. Often users of this type of closure element can be seen "slamming" the closure element into both the open and closed positions therefor. Since this manipulation is effected primarily through the handle, depending upon the relationship between the handle and the other working components of the latch mechanism, components of the latch mechanism may be highly stressed and prone to failure. This problem may become aggravated in the event that the closure element sticks, as may occur after excessive cycling of the closure element and/or in the event that damage is somehow inflicted thereon in use.
Designers and manufacturers of this type of closure element and latch system are also concerned with a number of other design considerations. It is commonly desirable to allow the handle to be repositioned in use by exerting a relatively constant force thereon throughout its operating range. Since it is common to spring bias the handle to one position therefor, a variable spring force may result as the handle is repositioned.
Designers and manufacturers also strive to design strike elements that function effectively and positively hold the closure element in a particular state, yet which are not obtrusive so as to be prone to being snagged by a user's clothing or other foreign objects. This is particularly a problem in the field of delivery vehicles in which users repeatedly enter and exit the vehicle to perform their jobs.
Another problem with this type of system, particularly in the delivery vehicle environment, is that of locking and unlocking the latch system while bearing packages. Typically, a lock system, used to maintain the latch system in the locked state, is incorporated which is manipulated separately from the handle that changes the latch assembly between the latched and unlatched states. This can make one-handed operation of the latch system, lock system and closure element difficult.
Conventional locking systems may also be constructed so that it is difficult to ascertain that the latch assembly is in a locked state. The user will often set the locking system and undertake trial and error to make certain that the locking system is properly operating. This may require that the user place the latch assembly in the released state and try to open the closure element. It is possible that if the closure element is for some reason jammed, the user may mistakenly conclude that the latch system is in the locked state.
Another potential problem with conventional latch systems is that with the latch system in the locked state, there may be a rigid interconnection between inside and outside components on the closure element which substantially fix the position of the outside handle. Attempted operation of the outside handle with the latch system in the locked state may impart damaging forces to components of the latch assembly or other parts of the mechanism. It is possible that the user of the system may conclude in an attempted operation thereof that the handle is jammed rather than locked, causing the user to exert an extraordinarily large force on the handle, with potentially damaging results.
Designers and manufacturers of this type of system also strive to produce handles that are accessible to be positively manipulated, yet which do not lend themselves to be grasped in such a manner as might tempt an individual to bear his/her own weight, i.e. to hang on the vehicle through the handle.
In some environments, it is desirable that the closure element be positively and releasably latched in each of two different positions, while at the same time allowing a user to conveniently, as with one hand, unlatch and draw the closure from each of the two positions to the other.